In recent years, damages on road pavement occurs and safety and comfortableness of traveling are lowered due to the increased amount of road traffic and of large-sized car traffic. Especially in road pavement of heavy traffic route line, many damages as rutting by flowing of asphalt, cracking, etc. are observed. In order to secure traffic safety, remedial work is performed frequently and, as a result, social problem is being caused. Moreover, if cracking occurs on road pavement, rainwater will permeate therefrom and it will result in hurting subbase course further and promoting cracking. In bridge deck pavement, water that permeates into reinforced concrete floor slab from on bridge deck through asphalt pavement not only makes steel rod and steel materials inside the floor slab corroded, but especially promotes degradation of concrete, and of the floor slab concrete under conditions of repeated load applied, and then load-carrying capacity and durability are adversely affected.
Various methods are proposed in order to improve these rutting and crack of road pavement. As a general method, a cutting overlay method in which asphalt effective in rutting that has high anti-flowability and high abrasion resistance, and asphalt effective in crack prevention that has high crack-proof property are used for asphalt pavement as an asphalt mixture maybe mentioned. However, at present, these methods offer neither effective solution for suppressing both of rutting and crack of asphalt pavement face nor large life extension of the paved road.
Moreover, various methods and compositions that reinforce overlay of asphalt pavement are proposed. For example, as shown in Japanese Patent Laid-Open No. 62-268413 or Japanese Patent Laid-Open No. 64-14415, there is so-called geotextile method. In geotextile method, geotextiles are applied on subgrade, subsequently granular material, such as banking materials or gravel, are applied thereon, and pavement subbase course is formed to disperse and support load applied on the pavement. However, in this method of construction, most effects over damage on rutting, crack, etc. that take place on asphalt pavement surface are not demonstrated.
Moreover, a method is proposed in which a shearing force inside asphalt mixture in asphalt pavement is restrained to reinforce asphalt mixture using geotextile. As examples aiming at improvement in reinforcement performance of asphalt mixture, for example, an example in which a grid comprising uniaxially/biaxially drawn material of synthetic resin is used, and an example in which a grid comprising strands with glass fiber impregnated with resins is used may be mentioned.
However, a drawn portion of the grid of this synthetic resin has quite a low tensile strength of 0.4 GPa, and then in order to reinforce asphalt mixture, quite a big basis weight is needed. Moreover, also in a grid using glass fiber, a defect is observed in which tensile strength falls by cutting of fiber by being worn and hooked at the time of paving asphalt.
Moreover, in these grids of glass fiber, or synthetic resin grid having high rigidity, in order to obtain high material strength, rigidity as a geotextile is set high. These geotextiles cannot be continuously rolled out at the time of application, and for this reason, difficulty in handling when applied is observed.
Besides, since this geotextile is used being inserted between lower layer and upper layer of asphalt, slide prevention and bonding strength between the upper layer and the lower layer need to be strengthened. Therefore, this geotextile has a form of grid. Consequently, it has a defect that decay of subbase course and subgrade by rainwater coming in via cracks that take place on asphalt pavement surface or damage portion cannot be prevented.
As a result of wholehearted research by the present inventors in order to solve the above described problem, it turned out that asphalt pavement is strengthened and permeation of rainwater etc. is effectively prevented by using a sheet for road reinforcement given in Japanese Patent Laid-Open No. 09-177014, and a big effect is demonstrated thereby to reflection crack and crack of asphalt surface course.
In the above described Japanese Patent, a sheet for road reinforcement has compatibility with asphalt pavement, at a temperature of asphalt mixture at the time of application (usually not less than 110° C.), asphalt of the sheet for road reinforcement melts, and forms a good plane for joint between asphalt pavement and the sheet, and unites with it. By this adhesive effect demonstrated, the sheet for road reinforcement can suppress a flow of asphalt pavement, and also can decrease a deflection of pavement material, resulting in suppression of phenomenon of rutting or crack. Consequently, it is indicated that the durability of not less than double is demonstrated compared with usual paved roads to phenomenon of crack or rutting observed on a road surface.
Besides, as shown in Japanese Patent Application No. 07-083678, a sheet for road reinforcement of this Japanese Patent Laid-open No. 09-177014 also has waterproofing function as a compound waterproofing sheet, and has reflection crack preventive ability, and also has waterproof ability for bridge deck pavement.
However, damage of asphalt pavement has become markedly increased due to increase in automobile traffic and enlargement of truck in recent years. Moreover, since requests to paved road from user of road or residents along the route is diversified, a pavement with special function in which outstanding durability, safety of traffic, environment, and cost reduction and long life are taken into consideration is desired, and therefore various multifunctional pavements are developed. As examples, drainage pavement with drainage function and noise reduction function, thin layer asphalt pavement, recycled improved asphalt mixture using recycled aggregates, and heated asphalt mixture in which slag of molten and cooled incinerated ashes of domestic wastes, crushed waste glass, waste plastic, piece of cutting of waste PET bottle, etc. are mixed as aggregate attract attention recently.
For example, a drainage pavement technical guiding principle (proposal) about drainage pavement is published, and in it asphalt with high viscosity is usually used as a binder of asphalt mixture used for a drainage pavement, and emulsified rubberized asphalt as tack coat.
Even if a sheet for road reinforcement given in Japanese Patent Laid-Open No. 09-177014 is used to an asphalt pavement using these asphalt mixtures, sufficient effect may not be demonstrated to crack and rutting that are formed in an asphalt pavement face.
The present inventors proceeded further a research about materials and methods for manufacturing, etc. that also support such various multifunctional pavements and that can also solve these problems.
The present invention is to offer a paved road that may cancel the above described defects.
One of the further large subjects of the present invention is decreasing an amount of asphalt used for pavement, i.e., enabling thin surfacing (thin layer pavement) with thickness of asphalt made thinner.
Thickness of asphalt used for pavement of road is indicated by various outlines and references. For example, according to MANUAL FOR ASPHALT PAVEMENT (1975 fiscal year version, 6–19 pages: Japan Road Association), thickness of surface asphalt is designed based on traffic of car;    A-case (less than 250 cars/day): Surface course asphalt 5 cm,    B-case (ibid. 250–1000 cars/day): Surface course asphalt 5 cm,    C-case (ibid. 1000–3000 cars/day): Surface course asphalt 10 cm,    D-case (not less than 3000 cars/day): Surface course asphalt 15 cm*. * Included binder course
Besides, according to asphalt pavement basic lecture; design of pavement of asphalt (Nichireki Kagaku Kogyo), it indicates that “generally, asphalt mixture is finished one layer up to 6 cm of thickness, and beyond it, finished in multilayered on the basis of 5 cm in thickness”, and also that “(as thickness of asphalt) surface course with a thickness of 5 cm on an upper subbage course may be made - - - omitting binder course, on the basis of 10 cm of standard for sum total of surface course and binder course, in the case where unit section automobile traffic is less than 2000 sets/day.”
Besides, although Japanese Patent Laid-Open No. 9-177014 is a patent using a reinforcement sheet and there is indicated that a strength of a road improves by use of a reinforcement sheet, but only an examination result of a road with a thickness of 5 cm is indicated in Example.
It was considered that it was very difficult to make a thickness of a surface course asphalt thinner than 5 cm from the above described design value etc. As described above, in road pavement, actual situation was that a subject was not taken into consideration in which a thickness is to be made thinner, based on old customs or regulations of construction outline etc. that surface course asphalt is to be not less than 5 cm.
It requires time of construction that thick asphalt is used, and huge quantity of asphalt is used for it.
Furthermore, in repair of a road, or reconstruction of asphalt, cutting of the asphalt is needed, and cutting generates noise and dust, therefore a great trouble is made to residents along the route, and legal restrictions are also applied about noise.
If asphalt used is thick, a long construction period will be required, and increase in an amount of cutting asphalt abandonment and construction period over a long period of time lead to problems in which influences on financial or environmental problems, such as traffic interception over a long period of time, bad environment for residents along the route, and high road repairing expense etc. become larger. It is very serious subject to mitigate these problems.